a.set_a {
    font-size: 18px;
    color: rgb(127, 127, 127);
}

a.set_a:hover {
    color: black;
}

.main-introduce {
    height: 650px;
    background: url(../images/background.png) no-repeat;
    background-position: center right;
    /* opacity: .5; */
    /* position: relative; */
    /* background: rgba(255,255,255,1);  */
}

.setpadding {
    padding-left: 35px;
}

a.set_btn_a,
a.set_btn_b {
    padding: 6px 16px;
    font-size: 24px;
    font-weight: 600;
    border-radius: 0;
    border: none;
}

.set_btn_a {
    background-color: #007BFF;
    margin-right: 20px;
}

.set_btn_a:hover {
    background-color: #0069D9;
}

.set_btn_b {
    background-color: darkgray;
}

.set_btn_b:hover {
    background-color: gray;
}
.set_btn_a:focus,
.set_btn_a:active,
.set_btn_b:focus,
.set_btn_b:active {
    box-shadow: none;
    outline: 0;
}

.introduce-part{
    height: 680px;
}        
.about-us{
    text-align: center;
    padding: 20px 0px;
}
.introduce-card {
    border: 1px solid lightgrey;
    border-radius: 6px;
    padding: 10px 0px;
    margin: 10px 0px;
    height: 250px;
}
.img_title{
    margin: 10px auto;
    margin-bottom: 30px;
}
.img_title img{
    margin-left: 148px;
}
.img_title h4{
    margin-top: 10px;
    text-align: center;
}
.introduce-text{
    text-align: center;
}

div.fixed-bottom{
    border-radius: 50%;
    position: fixed;
    left: 48%;
    bottom: 0;
    z-index: 99999;
    width: 60px;
    height: 60px;
}
div.fixed-bottom a{
    display: block;
    width: 100%;
    height: 100%;
}
.change-position{
    background: url(../images/xia.png) no-repeat;
    background-position: 6px 6px;
}